Most people are attracted to motorcycle riding not only because of the image it portrays, but also because of how the bike looks. Most modern motorcycles are beautifully engineered and beautiful to behold. Unfortunately it seems like the more athstetically pleasing a motorcycle is, the more CC's it has. When I first got the motorcycle bug, the one I dreamed about and saved up for was none other than the Honda CBR 1000RR!!!
Now THAT is a beautiful bike. Much like the North African spider monkey, that motorcycle is both beautiful, and deadly (in the wrong hands anyway). I'm not saying that as soon as you get on it you will die, and i'm also not saying that it is completely impossible to learn on that bike, but I AM saying that a bike with that much power behind it would be VERY hard to handle, especially if something unexpected happened like a child running across the street.
Let me preface this guide by saying that Yes, i know of people that have learned to ride motorcycles that are 1000cc's and greater, but it is definitely not something i'm going to reccomend. Generally these riders progress much slower than someone who starts off on a smaller machine like the Kawasaki Ninja 250. This is usually because they have to spend a lot of their focus on not grabbing too much throttle, and not grabbing too much brake, and trying to keep such a heavy and long machine on 2 wheels, especially during slow speed manuvers. On a motorcycle like the ninja though even if you do grab a fist full of throttle and twist it is much easier to recover, and the changes of lifting the front wheel off the ground are much lower. The brakes on smaller machines are also much more forgiving, although they should still be used carefully, THEY STOP YOU FAST!
So far we can see that a 600cc or greater motorcycle is not the perfect beginner motorcycle because it is a machine built for the race track. Another reason to get a smaller bike at first is the cost. A brand new Suzuki GSX 600 can run you $9,000+, that is a lot of clams, especially if you end up dropping it the first week (I've seen it happen). The Ninja 250 on the other hand only costs around $3,000 brand spanking new!! So if you do end up dropping it, its not going to be nearly as expensive to fix/replace parts.